The 2D limit equilibrium method is widely used for slope stability analysis.However,with the advancement of dump engineering,composite slopes often exhibit significant 3D mechanical effects.Consequently,it is of signi...The 2D limit equilibrium method is widely used for slope stability analysis.However,with the advancement of dump engineering,composite slopes often exhibit significant 3D mechanical effects.Consequently,it is of significant importance to develop an effective 3D stability calculation method for composite slopes to enhance the design and stability control of open-pit slope engineering.Using the composite slope formed by the mining stope and inner dump in Baiyinhua No.1 and No.2 open-pit coal mine as a case study,this research investigates the failure mode of composite slopes and establishes spatial shape equations for the sliding mass.By integrating the shear resistance and sliding force of each row of microstrip columns onto the bottom surface of the strip corresponding to the main sliding surface,a novel 2D equivalent physical and mechanical parameters analysis method for the strips on the main sliding surface of 3D sliding masses is proposed.Subsequently,a comprehensive 3D stability calculation method for composite slopes is developed,and the quantitative relationship between the coordinated development distance and its 3D stability coefficients is examined.The analysis reveals that the failure mode of the composite slope is characterized by cutting-bedding sliding,with the arc serving as the side interface and the weak layer as the bottom interface,while the destabilization mechanism primarily involves shear failure.The spatial form equation of the sliding mass comprises an ellipsoid and weak plane equation.The analysis revealed that when the coordinated development distance is 1500 m,the error rate between the 3D stability calculation result and the 2D stability calculation result of the composite slope is less than 8%,thereby verifying the proposed analytical method of equivalent physical and mechanical parameters and the 3D stability calculation method for composite slopes.Furthermore,the3D stability coefficient of the composite slope exhibits an exponential correlation with the coordinated development distance,with the coefficient gradually decreasing as the coordinated development distance increases.These findings provide a theoretical guideline for designing similar slope shape parameters and conducting stability analysis.展开更多
Background: As the population age structure gradually ages, more and more elderly people were found to have pulmonary nodules during physical examinations. Most elderly people had underlying diseases such as heart, lu...Background: As the population age structure gradually ages, more and more elderly people were found to have pulmonary nodules during physical examinations. Most elderly people had underlying diseases such as heart, lung, brain and blood vessels and cannot tolerate surgery. Computed tomography (CT)-guided percutaneous core needle biopsy (CNB) was the first choice for pathological diagnosis and subsequent targeted drugs, immune drugs or ablation treatment. CT-guided percutaneous CNB requires clinicians with rich CNB experience to ensure high CNB accuracy, but it was easy to cause complications such as pneumothorax and hemorrhage. Three-dimensional (3D) printing coplanar template (PCT) combined with CT-guided percutaneous pulmonary CNB biopsy has been used in clinical practice, but there was no prospective, randomized controlled study. Methods: Elderly patients with lung nodules admitted to the Department of Oncology of our hospital from January 2019 to January 2023 were selected. A total of 225 elderly patients were screened, and 30 patients were included after screening. They were randomly divided into experimental group (Group A: 30 cases) and control group (Group B: 30 cases). Group A was given 3D-PCT combined with CT-guided percutaneous pulmonary CNB biopsy, Group B underwent CT-guided percutaneous pulmonary CNB. The primary outcome measure of this study was the accuracy of diagnostic CNB, and the secondary outcome measures were CNB time, number of CNB needles, number of pathological tissues and complications. Results: The diagnostic accuracy of group A and group B was 96.67% and 76.67%, respectively (P = 0.026). There were statistical differences between group A and group B in average CNB time (P = 0.001), number of CNB (1 vs more than 1, P = 0.029), and pathological tissue obtained by CNB (3 vs 1, P = 0.040). There was no statistical difference in the incidence of pneumothorax and hemorrhage between the two groups (P > 0.05). Conclusions: 3D-PCT combined with CT-guided percutaneous CNB can improve the puncture accuracy of elderly patients, shorten the puncture time, reduce the number of punctures, and increase the amount of puncture pathological tissue, without increasing pneumothorax and hemorrhage complications. We look forward to verifying this in a phase III randomized controlled clinical study. .展开更多
This study proposes a hypodermic needle(HN)as a sorbent holder and an electrospray(ESI)emitter,thus combining extraction and analysis in a single device.A novel nylon 6-cellulose(N6-Cel)composite sorbent is proposed t...This study proposes a hypodermic needle(HN)as a sorbent holder and an electrospray(ESI)emitter,thus combining extraction and analysis in a single device.A novel nylon 6-cellulose(N6-Cel)composite sorbent is proposed to extract methadone from oral fluid samples.The cellulosic substrate provides the composite with high porosity,permitting the flow-through of the sample,while the polyamide contributes to the extraction of the analyte.The low price of the devices(considering the holder and the sorbent)contributes to the affordability of the method,and their small size allows easy transportation,opening the door to on-site extractions.Under the optimum conditions,the analyte can be determined by high-resolution ambient ionization mass spectrometry at a limit of detection(LOD)as low as 0.3 mg/L and precision(expressed as relative standard deviation,RSD)better than 9.3%.The trueness,expressed as relative recovery(RR),ranged from 90%to 109%.As high-resolution mass spectrometers are not available in many laboratories,the method was also adapted to low-resolution spectrometers.In this sense,the direct infusion of the eluates in a triple quadrupole-mass spectrometry provided an LOD of 2.2 mg/L.The RSD was better than 5.3%,and the RR ranged from 96%to 121%.展开更多
Silica fibers-reinforced, fused silica composites were fabricated with repeated vacuum-assisted liquid-phase infiltration. The mechanical properties, thermal properties, and ablative properties of the samples were eva...Silica fibers-reinforced, fused silica composites were fabricated with repeated vacuum-assisted liquid-phase infiltration. The mechanical properties, thermal properties, and ablative properties of the samples were evaluated. The effect of the silica fiber content and treatment temperature on the flexural strength of the three-dimensional SiO2 (3-D SiO2) composites also was investigated. The SiO2 composites show good mechanical properties and excellent ablative performance. The flexural strength increases with an increase in silica fiber content, and decreases with an increase in treatment temperature. When the volume fraction of the silica fiber is 50vo1% and the treatment temperature is 700℃ the flexural strength of the composites reaches a maximum value of 78 MPa. By adding cyclohexanone surfactant, the infiltration property can be largely improved, resulting in the density of SiO2 composites increasing up to 1.65 g/cm^3. The fracture surfaces of the flexural specimens observed using SEM, show that the pseudoplasticity and the toughening mechanisms of the composites are caused by absorption of a lot of energy by interface debonding and fiber pulling out.展开更多
Particulate-reinforced metal matrix composites(PRMMCs)are difficult to machine due to the inclusion of hard,brittle reinforcing particles.Existing experimental investigations rarely reveal the complex material removal...Particulate-reinforced metal matrix composites(PRMMCs)are difficult to machine due to the inclusion of hard,brittle reinforcing particles.Existing experimental investigations rarely reveal the complex material removal mechanisms(MRMs)involved in the machining of PRMMCs.This paper develops a three-dimensional(3D)microstructure-based model for investigating the MRM and surface integrity of machined PRMMCs.To accurately mimic the actual microstructure of a PRMMC,polyhedrons were randomly distributed inside the matrix to represent irregular SiC particles.Particle fracture and matrix deformation and failure were taken into account.For the model’s capability comparison,a two-dimensional(2D)analysis was also conducted.Relevant cutting experiments showed that the established 3D model accurately predicted the material removal,chip morphology,machined surface finish,and cutting forces.It was found that the matrix-particle-tool interactions led to particle fractures,mainly in the primary shear and secondary deformation zones along the cutting path and beneath the machined surface.Particle fracture and dilodegment greatly influences the quality of a machined surface.It was also found that although a 2D model can reflect certain material removal features,its ability to predict microstructural variation is limited.展开更多
Three-dimensional( 3 D) fabric composite is a newly developed sandwich structure,consisting of two identical parallel fabric decks woven integrally and mechanically together by means of vertical woven fabrics. In this...Three-dimensional( 3 D) fabric composite is a newly developed sandwich structure,consisting of two identical parallel fabric decks woven integrally and mechanically together by means of vertical woven fabrics. In this paper,six types of 3 D fabric sandwich composites were developed in terms of compressive and flexural properties as a function of pile height( 10, 20 and30 mm) and pile distance( 16, 24 and 32 mm) in pile structures. The mechanical characteristics and the damage modes of the 3 D fabric sandwich composites under compressive and flexural load conditions were investigated. Besides,the influence of pile height and pile distance on the 3 D fabric sandwich composites mechanical properties was analyzed. The results showed that the compressive properties decreased with the increase of the pile height and the pile distance. Flexural properties increased with the increase of pile height, while decreased with the increase of pile distance.展开更多
The effects of fiber volume fraction on damping properties of carbon fiber three-dimensional and five-directional( 3D-5Dir)braided carbon fiber / epoxyres in composite cantilever beams were studied by experimental mod...The effects of fiber volume fraction on damping properties of carbon fiber three-dimensional and five-directional( 3D-5Dir)braided carbon fiber / epoxyres in composite cantilever beams were studied by experimental modal analysis method. Meanwhile,carbon fiber plain woven laminated / epoxy resin composites with different fiber volume fraction were concerned for comparison. The experimental result of braided specimens shows that the first three orders of natural frequency increase and the first three orders of the damping ratios of specimens decrease, when the fiber volume fraction increases. Furthermore,larger fiber volume fraction will be valuable for the better anti-exiting property of braided composites,and get an opposite effect on dissipation of vibration energy. The fiber volume fraction is an important factor for vibration performance design of braided composites. The comparison between the braided specimens and laminated specimens reveals that 3D braided composites have a wider range of damping properties than laminated composites with the same fiber volume fractions.展开更多
This work provides a method to predict the three-dimensional equivalent elastic properties of the filament-wound composites based on the multi-scale homogenization principle.In the meso-scale,a representative volume e...This work provides a method to predict the three-dimensional equivalent elastic properties of the filament-wound composites based on the multi-scale homogenization principle.In the meso-scale,a representative volume element(RVE)is defined and the bridging model is adopted to establish a theoretical predictive model for its three-dimensional equivalent elastic constants.The results obtained through this method for the previous experimental model are compared with the ones gained respectively by experiments and classical laminate theory to verify the reliability of this model.In addition,the effects of some winding parameters,such as winding angle,on the equivalent elastic behavior of the filament-wound composites are analyzed.The rules gained can provide a theoretical reference for the optimum design of filament-wound composites.展开更多
To improve the specific capacitance and rate capability of electrode material for supercapacitors, a three-dimensional graphene/polyaniline (3DGN/PANI) composite is prepared via in situ polymerization on GN hydrogel...To improve the specific capacitance and rate capability of electrode material for supercapacitors, a three-dimensional graphene/polyaniline (3DGN/PANI) composite is prepared via in situ polymerization on GN hydrogel. PANI grows on the GN surface as a thin film, and its content in the composite is controlled by the concentration of the reaction monomer. The specific capacitance of the 3DGN/PANI composite containing 10 wt% PANI reaches 322.8 F.g-1 at a current density of 1 A.g-1, nearly twice as large as that of the pure 3DGN (162.8 F.g-1). The capacitance of the composite is 307.9 F.g-1 at 30 A.g-1 (maintaining 95.4%), and 89% retention after 500 cycles. This study demonstrates the exciting potential of 3DGN/PANI with high capacitance, excellent rate capability and long cycling life for supercapacitors.展开更多
As a thermosetting resin with excellent properties,epoxy resin is used in many areas such as electronics,transportation,aerospace,and other fields.However,its relatively low thermal conductivity limits its wide applic...As a thermosetting resin with excellent properties,epoxy resin is used in many areas such as electronics,transportation,aerospace,and other fields.However,its relatively low thermal conductivity limits its wide application in more demanding fields.Here,a three-dimensional carbon(3DC)network was prepared through NaCl template-assisted in situ chemical vapor deposition(CVD)and used to reinforce epoxy resin for enhancing its thermal conductivity.The 3DC was prepared with a molar ratio of sodium atom to carbon atom of 100:20,and argon atmosphere in CVD led to an optimal improvement in the thermal conductivity of epoxy resin.The thermal conductivity of epoxy resin increased by 18%when the filling content was 3 wt.%of 3DC network because of the high contact area,uniform dispersion,and enhanced formation of conductive paths with epoxy resin.As the amount of 3DC addition increases,the thermal conductivity of composites also increases.As an innovative exploration,the work presented in this paper is of great significance for the thermal conductivity application of epoxy resin in the future.展开更多
Three-dimensional(3D)braided composites with better properties have been used in some particular industries.Some have had obvious signs of crack when they are braided.Others have had catastrophic failures occuring wit...Three-dimensional(3D)braided composites with better properties have been used in some particular industries.Some have had obvious signs of crack when they are braided.Others have had catastrophic failures occuring without warning.A new methodology for the analysis of failure modes in composite materials by means of acoustic emission techniques has been developed.The occurrence of fiber-breakage during tensile loading tests has been observed by the acoustic emission technology.Using acoustic emission technology is investigated as a means of monitoring 3D braided composites structures,detecting damage,and predicting impending damage.Some of the findings of the research project were presented.展开更多
Quasi-static and dynamic mechanical properties of glass-fiber reinforced polymer composites embedded with and without tetraneedle-shaped ZnO whiskers(T-ZnOw)in two loading directions are investigated by a split Hopkin...Quasi-static and dynamic mechanical properties of glass-fiber reinforced polymer composites embedded with and without tetraneedle-shaped ZnO whiskers(T-ZnOw)in two loading directions are investigated by a split Hopkinson pressure bar.The stress-strain curves,ultimate strength,failure strain and elastic modulus are obtained and the failure mechanism of the composites is investigated by a high-speed camera and a scanning electron microscope.Strain rate effects on the mechanical behavior are discussed and the corresponding models are derived by fitting the experimental data.The experimental results show that the composites with T-ZnOw under dynamic loading have multiple failure modes and better mechanical properties.Finally,the strengthening and toughening mechanisms of T-ZnOw are analyzed.It is shown that T-ZnOw can improve mechanical properties of the composites,and can make the composites have some new features.The present results provide a reliable basis for advanced composite design and manufacture,and have broad applications in the field of aerospace.展开更多
Electrospinning is a powerful method for fabricating micro/nano fibers that can be applied to various fields.Composite materials with nanoscale structure can show more excellent properties than their conventional part...Electrospinning is a powerful method for fabricating micro/nano fibers that can be applied to various fields.Composite materials with nanoscale structure can show more excellent properties than their conventional partners.Here,we reported hierarchical structured nanofibers with beads and spheres by double needle electrospinning with an auxiliary airflow.Two different spinning solutions with different concentrations were placed into different syringes.The action of airflow was able to make the two differently morphological nanofibers mixed together evenly.The results showed that the obtained nanofiber membrane has a good hierarchical structure with different morphologies.展开更多
The influence of the processing parameters on the properties of needle-punched composite geotextiles,compounded by polypropylene filament woven-fabrics and nonwoven fabrics is studied by using orthogonal design method...The influence of the processing parameters on the properties of needle-punched composite geotextiles,compounded by polypropylene filament woven-fabrics and nonwoven fabrics is studied by using orthogonal design method. The relationship between tensile strength and peeling strength is discussed. The experimental results are offered as reference.展开更多
A three-dimensional dynamic damage model that fits both small and large damage sizes is developed to predict impact damage initiation and propagation for each lamina of T300-carbon/epoxy laminations.First,13 specimens...A three-dimensional dynamic damage model that fits both small and large damage sizes is developed to predict impact damage initiation and propagation for each lamina of T300-carbon/epoxy laminations.First,13 specimens of the same lamination sequence are subjected to three different impact energies(10 J,15 J,and 20 J).After the impact,the laminates are inspected by the naked eye to observe the damage in the outer layers,and subsequently X-rayed to detect the inner damage.Next,the stress analysis of laminates subjected to impact loading is presented,based on the Hertz contact law and virtual displacement principle.Based on the analysis results,a three-dimensional dynamic damage model is proposed,including the Hou failure criteria and Camanho stiffness degradation model,to predict the impact damage shape and area.The numerical predictions of the damage shape and area show a relatively reasonable agreement with the experiments.Finally,the impact damage initiation and propagation for each lamina are investigated using this damage model,and the results improve the understanding of the impact process.展开更多
The development of graphene-based composites with low density,robust absorption,wide bandwidth and thin thickness remained a great challenge in the field of electromagnetic(EM)absorption.In this work,nitrogen-doped re...The development of graphene-based composites with low density,robust absorption,wide bandwidth and thin thickness remained a great challenge in the field of electromagnetic(EM)absorption.In this work,nitrogen-doped reduced graphene oxide/hollow cobalt ferrite(NRGO/hollow CoFe_(2)O_(4))composite aerogels were constructed by a solvothermal and hydrothermal two-step route.Results demonstrated that the as-fabricated composite aerogels had the ultralow density and a unique three-dimensional(3D)network structure,and lots of hollow CoFe_(2)O_(4)microspheres were almost homogeneously distributed on the wrinkled surfaces of lamellar NRGO.Moreover,superior EM absorbing capacity could be achieved by modulating the ferrite structure,addition amounts of hollow CoFe_(2)O_(4)and thicknesses.It was noteworthy that the NRGO/hollow CoFe_(2)O_(4)composite aerogel with the addition amount of ferrite of 15.0 mg pos-sessed the minimum reflection loss of-44.7 dB and maximum absorption bandwidth of 5.2 GHz(from 12.6 to 17.8 GHz)at a very thin thickness of 1.8 mm and filling ratio of 15.0 wt.%.Furthermore,the possible EM attenuation mechanism had been proposed.The results of this work would be helpful for developing RGO-based 3D composites as lightweight,thin and highly efficient EM wave absorbers.展开更多
Using AVISO satellite altimeter observations during 1993–2015 and a manual eddy detection method, a total of 276 anticyclonic rings and 242 cyclonic rings shed from the Kuroshio Extension(KE) were identified, and the...Using AVISO satellite altimeter observations during 1993–2015 and a manual eddy detection method, a total of 276 anticyclonic rings and 242 cyclonic rings shed from the Kuroshio Extension(KE) were identified, and their three-dimensional(3D) anomaly structures were further reconstructd based on the Argo float data and the Japan Agency for Marine-Earth Science and Technology(JAMSTEC) cruise and buoy data through an interpolation method. It is found that the cyclonic(anticyclonic) rings presented consistent negative(positive) anomalies of potential temperature;meanwhile the relevant maximum anomaly center became increasingly shallow for the cyclonic rings whereas it went deeper for the anticyclonic rings as the potential temperature anomaly decreased from the west to the east. The above deepening or shoaling trend is associated with the zonal change of the depth of the main thermocline. Moreover, the composite cold ring between 140° and 150°E was found to exhibit a double-core vertical structure due to the existence of mode water with low potential vorticity. Specifically, a relatively large negative(positive) salinity anomaly and a small positive(negative) one appeared for the composite cyclonic(anticyclonic) ring at the depth above and below 600 m, respectively. The underlying driving force for the temperature and salinity anomaly of the composite rings was also attempted, which varies depending on the intensity of the background current and the temperature and salinity fields in different areas of the KE region, and the rings’ influences on the temperature and salinity could reach deeper than 1 000 m on average.展开更多
This paper describes a study of three-dimensional braids produced by a four-step 1 × 1 method. An analytical approach is employed in conjunction with experimental investigations to establish the relationship betw...This paper describes a study of three-dimensional braids produced by a four-step 1 × 1 method. An analytical approach is employed in conjunction with experimental investigations to establish the relationship between the braid structure and braiding parameters. Based on microscopic observations, we divide a three-dimensional braid structure into three representative regions, i.e., the interior, surface and corner, and treat the three regions, respectively. Three types of microstructural unit-cell models are then established. The surface characteristics and the relationship between the interior and surface unit-cells have been derived. Good agreement has been obtained between the calculated and measured values of fiber volume fraction of the braided composite samples.展开更多
In view of rite effective elastic moduli theory([1]), analyzing the thick composite laminated bars subjected to an externally applied torque are presented by three-dimensional finite element (3-D FEM) and global-local...In view of rite effective elastic moduli theory([1]), analyzing the thick composite laminated bars subjected to an externally applied torque are presented by three-dimensional finite element (3-D FEM) and global-local method in this paper. Numerical results involving the distribution of shearing stresses olt cross-section and the torsional deformation and the interlaminar stresses near to free edges are given. If necessary elements discretization may be densely carried out only in the high stress gradient, region. Obviously, it requires less computer memory and computational time so that it offers an effective way for evaluating strength of laminated bars torsion with a greet number of layers.展开更多
基金supported by the National Natural Science Foundation of China (No.52374124)National Youth Science Foundation of China (No.52204135)+3 种基金Xing Liao Talent Plan (No.XLYC2202004)Young Elite Scientists Sponsorship Program by CAST (No.2023QNRC001)Liaoning Province International Science and Technology Cooperation Plan (No.2022JH2/1070004)Liaoning Natural Science Foundation Program (No.2022-BS-327)。
文摘The 2D limit equilibrium method is widely used for slope stability analysis.However,with the advancement of dump engineering,composite slopes often exhibit significant 3D mechanical effects.Consequently,it is of significant importance to develop an effective 3D stability calculation method for composite slopes to enhance the design and stability control of open-pit slope engineering.Using the composite slope formed by the mining stope and inner dump in Baiyinhua No.1 and No.2 open-pit coal mine as a case study,this research investigates the failure mode of composite slopes and establishes spatial shape equations for the sliding mass.By integrating the shear resistance and sliding force of each row of microstrip columns onto the bottom surface of the strip corresponding to the main sliding surface,a novel 2D equivalent physical and mechanical parameters analysis method for the strips on the main sliding surface of 3D sliding masses is proposed.Subsequently,a comprehensive 3D stability calculation method for composite slopes is developed,and the quantitative relationship between the coordinated development distance and its 3D stability coefficients is examined.The analysis reveals that the failure mode of the composite slope is characterized by cutting-bedding sliding,with the arc serving as the side interface and the weak layer as the bottom interface,while the destabilization mechanism primarily involves shear failure.The spatial form equation of the sliding mass comprises an ellipsoid and weak plane equation.The analysis revealed that when the coordinated development distance is 1500 m,the error rate between the 3D stability calculation result and the 2D stability calculation result of the composite slope is less than 8%,thereby verifying the proposed analytical method of equivalent physical and mechanical parameters and the 3D stability calculation method for composite slopes.Furthermore,the3D stability coefficient of the composite slope exhibits an exponential correlation with the coordinated development distance,with the coefficient gradually decreasing as the coordinated development distance increases.These findings provide a theoretical guideline for designing similar slope shape parameters and conducting stability analysis.
文摘Background: As the population age structure gradually ages, more and more elderly people were found to have pulmonary nodules during physical examinations. Most elderly people had underlying diseases such as heart, lung, brain and blood vessels and cannot tolerate surgery. Computed tomography (CT)-guided percutaneous core needle biopsy (CNB) was the first choice for pathological diagnosis and subsequent targeted drugs, immune drugs or ablation treatment. CT-guided percutaneous CNB requires clinicians with rich CNB experience to ensure high CNB accuracy, but it was easy to cause complications such as pneumothorax and hemorrhage. Three-dimensional (3D) printing coplanar template (PCT) combined with CT-guided percutaneous pulmonary CNB biopsy has been used in clinical practice, but there was no prospective, randomized controlled study. Methods: Elderly patients with lung nodules admitted to the Department of Oncology of our hospital from January 2019 to January 2023 were selected. A total of 225 elderly patients were screened, and 30 patients were included after screening. They were randomly divided into experimental group (Group A: 30 cases) and control group (Group B: 30 cases). Group A was given 3D-PCT combined with CT-guided percutaneous pulmonary CNB biopsy, Group B underwent CT-guided percutaneous pulmonary CNB. The primary outcome measure of this study was the accuracy of diagnostic CNB, and the secondary outcome measures were CNB time, number of CNB needles, number of pathological tissues and complications. Results: The diagnostic accuracy of group A and group B was 96.67% and 76.67%, respectively (P = 0.026). There were statistical differences between group A and group B in average CNB time (P = 0.001), number of CNB (1 vs more than 1, P = 0.029), and pathological tissue obtained by CNB (3 vs 1, P = 0.040). There was no statistical difference in the incidence of pneumothorax and hemorrhage between the two groups (P > 0.05). Conclusions: 3D-PCT combined with CT-guided percutaneous CNB can improve the puncture accuracy of elderly patients, shorten the puncture time, reduce the number of punctures, and increase the amount of puncture pathological tissue, without increasing pneumothorax and hemorrhage complications. We look forward to verifying this in a phase III randomized controlled clinical study. .
基金The grant“Biopolymer substrates for the determination of opioids in biofluids by ambient mass spectrometry”(Grant No.:PID2020-112862RB-I00)funded by MCIN/AEI/10.13039/501100011033(Feder“Una manera de hacer Europa”)is gratefully acknowledged。
文摘This study proposes a hypodermic needle(HN)as a sorbent holder and an electrospray(ESI)emitter,thus combining extraction and analysis in a single device.A novel nylon 6-cellulose(N6-Cel)composite sorbent is proposed to extract methadone from oral fluid samples.The cellulosic substrate provides the composite with high porosity,permitting the flow-through of the sample,while the polyamide contributes to the extraction of the analyte.The low price of the devices(considering the holder and the sorbent)contributes to the affordability of the method,and their small size allows easy transportation,opening the door to on-site extractions.Under the optimum conditions,the analyte can be determined by high-resolution ambient ionization mass spectrometry at a limit of detection(LOD)as low as 0.3 mg/L and precision(expressed as relative standard deviation,RSD)better than 9.3%.The trueness,expressed as relative recovery(RR),ranged from 90%to 109%.As high-resolution mass spectrometers are not available in many laboratories,the method was also adapted to low-resolution spectrometers.In this sense,the direct infusion of the eluates in a triple quadrupole-mass spectrometry provided an LOD of 2.2 mg/L.The RSD was better than 5.3%,and the RR ranged from 96%to 121%.
文摘Silica fibers-reinforced, fused silica composites were fabricated with repeated vacuum-assisted liquid-phase infiltration. The mechanical properties, thermal properties, and ablative properties of the samples were evaluated. The effect of the silica fiber content and treatment temperature on the flexural strength of the three-dimensional SiO2 (3-D SiO2) composites also was investigated. The SiO2 composites show good mechanical properties and excellent ablative performance. The flexural strength increases with an increase in silica fiber content, and decreases with an increase in treatment temperature. When the volume fraction of the silica fiber is 50vo1% and the treatment temperature is 700℃ the flexural strength of the composites reaches a maximum value of 78 MPa. By adding cyclohexanone surfactant, the infiltration property can be largely improved, resulting in the density of SiO2 composites increasing up to 1.65 g/cm^3. The fracture surfaces of the flexural specimens observed using SEM, show that the pseudoplasticity and the toughening mechanisms of the composites are caused by absorption of a lot of energy by interface debonding and fiber pulling out.
文摘Particulate-reinforced metal matrix composites(PRMMCs)are difficult to machine due to the inclusion of hard,brittle reinforcing particles.Existing experimental investigations rarely reveal the complex material removal mechanisms(MRMs)involved in the machining of PRMMCs.This paper develops a three-dimensional(3D)microstructure-based model for investigating the MRM and surface integrity of machined PRMMCs.To accurately mimic the actual microstructure of a PRMMC,polyhedrons were randomly distributed inside the matrix to represent irregular SiC particles.Particle fracture and matrix deformation and failure were taken into account.For the model’s capability comparison,a two-dimensional(2D)analysis was also conducted.Relevant cutting experiments showed that the established 3D model accurately predicted the material removal,chip morphology,machined surface finish,and cutting forces.It was found that the matrix-particle-tool interactions led to particle fractures,mainly in the primary shear and secondary deformation zones along the cutting path and beneath the machined surface.Particle fracture and dilodegment greatly influences the quality of a machined surface.It was also found that although a 2D model can reflect certain material removal features,its ability to predict microstructural variation is limited.
基金National Key R&D Program of China(Nos.2016YFB0303104,2018YFC0810306)Jiangsu Overseas Visiting Scholar Program for University Prominent Younge Middle-aged Teachers and PresidentsSix Talent Peaks Project in Jiangsu Province,China(No.XCL-061)
文摘Three-dimensional( 3 D) fabric composite is a newly developed sandwich structure,consisting of two identical parallel fabric decks woven integrally and mechanically together by means of vertical woven fabrics. In this paper,six types of 3 D fabric sandwich composites were developed in terms of compressive and flexural properties as a function of pile height( 10, 20 and30 mm) and pile distance( 16, 24 and 32 mm) in pile structures. The mechanical characteristics and the damage modes of the 3 D fabric sandwich composites under compressive and flexural load conditions were investigated. Besides,the influence of pile height and pile distance on the 3 D fabric sandwich composites mechanical properties was analyzed. The results showed that the compressive properties decreased with the increase of the pile height and the pile distance. Flexural properties increased with the increase of pile height, while decreased with the increase of pile distance.
基金Tianjin Municipal Science and Technologies Commission,China(Nos.10SYSYJC27800,1ZCKFSF00500)
文摘The effects of fiber volume fraction on damping properties of carbon fiber three-dimensional and five-directional( 3D-5Dir)braided carbon fiber / epoxyres in composite cantilever beams were studied by experimental modal analysis method. Meanwhile,carbon fiber plain woven laminated / epoxy resin composites with different fiber volume fraction were concerned for comparison. The experimental result of braided specimens shows that the first three orders of natural frequency increase and the first three orders of the damping ratios of specimens decrease, when the fiber volume fraction increases. Furthermore,larger fiber volume fraction will be valuable for the better anti-exiting property of braided composites,and get an opposite effect on dissipation of vibration energy. The fiber volume fraction is an important factor for vibration performance design of braided composites. The comparison between the braided specimens and laminated specimens reveals that 3D braided composites have a wider range of damping properties than laminated composites with the same fiber volume fractions.
文摘This work provides a method to predict the three-dimensional equivalent elastic properties of the filament-wound composites based on the multi-scale homogenization principle.In the meso-scale,a representative volume element(RVE)is defined and the bridging model is adopted to establish a theoretical predictive model for its three-dimensional equivalent elastic constants.The results obtained through this method for the previous experimental model are compared with the ones gained respectively by experiments and classical laminate theory to verify the reliability of this model.In addition,the effects of some winding parameters,such as winding angle,on the equivalent elastic behavior of the filament-wound composites are analyzed.The rules gained can provide a theoretical reference for the optimum design of filament-wound composites.
基金Project supported by the National Basic Research Program of China(Grant Nos.2011CB932700 and 2011CB932703)the National Natural Science Foundation of China(Grant Nos.61335006,61378073,and 61077044)+1 种基金the Beijing Natural Science Foundation,China(Grant No.4132031)the Fundamental Research Funds for the Central Universities of Beijing Jiaotong University,China(Grant No.2014YJS136)
文摘To improve the specific capacitance and rate capability of electrode material for supercapacitors, a three-dimensional graphene/polyaniline (3DGN/PANI) composite is prepared via in situ polymerization on GN hydrogel. PANI grows on the GN surface as a thin film, and its content in the composite is controlled by the concentration of the reaction monomer. The specific capacitance of the 3DGN/PANI composite containing 10 wt% PANI reaches 322.8 F.g-1 at a current density of 1 A.g-1, nearly twice as large as that of the pure 3DGN (162.8 F.g-1). The capacitance of the composite is 307.9 F.g-1 at 30 A.g-1 (maintaining 95.4%), and 89% retention after 500 cycles. This study demonstrates the exciting potential of 3DGN/PANI with high capacitance, excellent rate capability and long cycling life for supercapacitors.
基金the Key Projects of Tianjin Natural Science Foundation(No.16ZXCLGX00130).
文摘As a thermosetting resin with excellent properties,epoxy resin is used in many areas such as electronics,transportation,aerospace,and other fields.However,its relatively low thermal conductivity limits its wide application in more demanding fields.Here,a three-dimensional carbon(3DC)network was prepared through NaCl template-assisted in situ chemical vapor deposition(CVD)and used to reinforce epoxy resin for enhancing its thermal conductivity.The 3DC was prepared with a molar ratio of sodium atom to carbon atom of 100:20,and argon atmosphere in CVD led to an optimal improvement in the thermal conductivity of epoxy resin.The thermal conductivity of epoxy resin increased by 18%when the filling content was 3 wt.%of 3DC network because of the high contact area,uniform dispersion,and enhanced formation of conductive paths with epoxy resin.As the amount of 3DC addition increases,the thermal conductivity of composites also increases.As an innovative exploration,the work presented in this paper is of great significance for the thermal conductivity application of epoxy resin in the future.
基金Tianjin Natural Science Sustentation Fund Project,China(No.043600711)Ministry of Education Sustentation Fund Project,China(No.03008)
文摘Three-dimensional(3D)braided composites with better properties have been used in some particular industries.Some have had obvious signs of crack when they are braided.Others have had catastrophic failures occuring without warning.A new methodology for the analysis of failure modes in composite materials by means of acoustic emission techniques has been developed.The occurrence of fiber-breakage during tensile loading tests has been observed by the acoustic emission technology.Using acoustic emission technology is investigated as a means of monitoring 3D braided composites structures,detecting damage,and predicting impending damage.Some of the findings of the research project were presented.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10672020 and 50742007.
文摘Quasi-static and dynamic mechanical properties of glass-fiber reinforced polymer composites embedded with and without tetraneedle-shaped ZnO whiskers(T-ZnOw)in two loading directions are investigated by a split Hopkinson pressure bar.The stress-strain curves,ultimate strength,failure strain and elastic modulus are obtained and the failure mechanism of the composites is investigated by a high-speed camera and a scanning electron microscope.Strain rate effects on the mechanical behavior are discussed and the corresponding models are derived by fitting the experimental data.The experimental results show that the composites with T-ZnOw under dynamic loading have multiple failure modes and better mechanical properties.Finally,the strengthening and toughening mechanisms of T-ZnOw are analyzed.It is shown that T-ZnOw can improve mechanical properties of the composites,and can make the composites have some new features.The present results provide a reliable basis for advanced composite design and manufacture,and have broad applications in the field of aerospace.
文摘Electrospinning is a powerful method for fabricating micro/nano fibers that can be applied to various fields.Composite materials with nanoscale structure can show more excellent properties than their conventional partners.Here,we reported hierarchical structured nanofibers with beads and spheres by double needle electrospinning with an auxiliary airflow.Two different spinning solutions with different concentrations were placed into different syringes.The action of airflow was able to make the two differently morphological nanofibers mixed together evenly.The results showed that the obtained nanofiber membrane has a good hierarchical structure with different morphologies.
文摘The influence of the processing parameters on the properties of needle-punched composite geotextiles,compounded by polypropylene filament woven-fabrics and nonwoven fabrics is studied by using orthogonal design method. The relationship between tensile strength and peeling strength is discussed. The experimental results are offered as reference.
文摘A three-dimensional dynamic damage model that fits both small and large damage sizes is developed to predict impact damage initiation and propagation for each lamina of T300-carbon/epoxy laminations.First,13 specimens of the same lamination sequence are subjected to three different impact energies(10 J,15 J,and 20 J).After the impact,the laminates are inspected by the naked eye to observe the damage in the outer layers,and subsequently X-rayed to detect the inner damage.Next,the stress analysis of laminates subjected to impact loading is presented,based on the Hertz contact law and virtual displacement principle.Based on the analysis results,a three-dimensional dynamic damage model is proposed,including the Hou failure criteria and Camanho stiffness degradation model,to predict the impact damage shape and area.The numerical predictions of the damage shape and area show a relatively reasonable agreement with the experiments.Finally,the impact damage initiation and propagation for each lamina are investigated using this damage model,and the results improve the understanding of the impact process.
基金supported by the Foundation of Provincial Natural Science Research Project of Anhui Colleges(No.KJ2021ZD0047)the Anhui Provincial Natural Science Foundation(No.2008085J27)+1 种基金the China Postdoctoral Science Foundation(No.2019M652160)the Research Foundation of the Institute of Environment-friendly Materials and Occupational Health(Wuhu),Anhui University of Science and Technology(No.ALW2020YF05).
文摘The development of graphene-based composites with low density,robust absorption,wide bandwidth and thin thickness remained a great challenge in the field of electromagnetic(EM)absorption.In this work,nitrogen-doped reduced graphene oxide/hollow cobalt ferrite(NRGO/hollow CoFe_(2)O_(4))composite aerogels were constructed by a solvothermal and hydrothermal two-step route.Results demonstrated that the as-fabricated composite aerogels had the ultralow density and a unique three-dimensional(3D)network structure,and lots of hollow CoFe_(2)O_(4)microspheres were almost homogeneously distributed on the wrinkled surfaces of lamellar NRGO.Moreover,superior EM absorbing capacity could be achieved by modulating the ferrite structure,addition amounts of hollow CoFe_(2)O_(4)and thicknesses.It was noteworthy that the NRGO/hollow CoFe_(2)O_(4)composite aerogel with the addition amount of ferrite of 15.0 mg pos-sessed the minimum reflection loss of-44.7 dB and maximum absorption bandwidth of 5.2 GHz(from 12.6 to 17.8 GHz)at a very thin thickness of 1.8 mm and filling ratio of 15.0 wt.%.Furthermore,the possible EM attenuation mechanism had been proposed.The results of this work would be helpful for developing RGO-based 3D composites as lightweight,thin and highly efficient EM wave absorbers.
基金The National Key Research and Development Program of China under contract No. 2016YFC1402607Scientific Research Foundation of Third Institude of Oceanography, Ministry of Nature Resources under contract Nos 2017012 and 2018001Global Change and Air-Sea Interaction Program under contract Nos GASI-IPOVAI-02 and GASI-IPOVAI-03.
文摘Using AVISO satellite altimeter observations during 1993–2015 and a manual eddy detection method, a total of 276 anticyclonic rings and 242 cyclonic rings shed from the Kuroshio Extension(KE) were identified, and their three-dimensional(3D) anomaly structures were further reconstructd based on the Argo float data and the Japan Agency for Marine-Earth Science and Technology(JAMSTEC) cruise and buoy data through an interpolation method. It is found that the cyclonic(anticyclonic) rings presented consistent negative(positive) anomalies of potential temperature;meanwhile the relevant maximum anomaly center became increasingly shallow for the cyclonic rings whereas it went deeper for the anticyclonic rings as the potential temperature anomaly decreased from the west to the east. The above deepening or shoaling trend is associated with the zonal change of the depth of the main thermocline. Moreover, the composite cold ring between 140° and 150°E was found to exhibit a double-core vertical structure due to the existence of mode water with low potential vorticity. Specifically, a relatively large negative(positive) salinity anomaly and a small positive(negative) one appeared for the composite cyclonic(anticyclonic) ring at the depth above and below 600 m, respectively. The underlying driving force for the temperature and salinity anomaly of the composite rings was also attempted, which varies depending on the intensity of the background current and the temperature and salinity fields in different areas of the KE region, and the rings’ influences on the temperature and salinity could reach deeper than 1 000 m on average.
文摘This paper describes a study of three-dimensional braids produced by a four-step 1 × 1 method. An analytical approach is employed in conjunction with experimental investigations to establish the relationship between the braid structure and braiding parameters. Based on microscopic observations, we divide a three-dimensional braid structure into three representative regions, i.e., the interior, surface and corner, and treat the three regions, respectively. Three types of microstructural unit-cell models are then established. The surface characteristics and the relationship between the interior and surface unit-cells have been derived. Good agreement has been obtained between the calculated and measured values of fiber volume fraction of the braided composite samples.
文摘In view of rite effective elastic moduli theory([1]), analyzing the thick composite laminated bars subjected to an externally applied torque are presented by three-dimensional finite element (3-D FEM) and global-local method in this paper. Numerical results involving the distribution of shearing stresses olt cross-section and the torsional deformation and the interlaminar stresses near to free edges are given. If necessary elements discretization may be densely carried out only in the high stress gradient, region. Obviously, it requires less computer memory and computational time so that it offers an effective way for evaluating strength of laminated bars torsion with a greet number of layers.